1. Field of the Invention
This invention relates to a cross connect frame for digital signals (hereinafter referred to as a "DSX") and more particularly to a DSX which allows enhanced electronic features to be combined with traditional electromechanical features in a unit which takes up no more floor space than one with only the traditional features.
2. Description of the Prior Art
The DSX, as specified in the Compatability Bulletin No. 119 of the American Telegraph and Telephone Co., is that intermediate terminating point where DS-1 equipment such as multiplexers, channel banks, switches and transmission facilities can be interconnected. In the electromechanical form in which the DSX is presently embodied in the prior art it typically consists of a steel frame upon which is mounted two sets of terminal blocks. The transmission facilities, i.e., the digital transmission lines entering the office where the DSX is located and the digital equipment in that office, are connected to one of the sets of blocks and that set and its blocks will be referred to as the "line" and "equipment" blocks, as the case may be. The other set is used for the cross connection and its blocks will be referred to as the "cross-connect" blocks. The electromechanical DSX is generally used to perform the cross connection between the line and equipment facilities.
Also mounted on the electromechanical DSX steel frame is a jackfield. The jacks are wired such that they can be used either for test access or for temporarily effecting a cross-connection also known as "patching". Patching is possible even if there is a previously wired cross-connection as the insertion of a plug in a jack causes a set of contacts to open to thereby break the connection between the equipment and cross-connect blocks. Insertion of the plug into a jack also connects the tip and ring conductors of the plug to the corresponding leads on the equipment block to which the jack is wired. If the plug should be part of a cable or patch cord assembly which has a like plug on the other end, then the insertion of the other plug into another jack also connects the tip and ring conductors of the plug to the leads on the equipment block to which that jack is wired. The insertion of the plugs into the jacks breaks any previously wired connection between the equipment and cross-connect blocks. The patch cord then connects the equipment leads to each other thereby by passing any previously wired connection.
Since the DSX is used to connect digital facilities which are operating at data rates in excess of one megabit per second (Mbps), they are specially constructed to minimize crosstalk. Aside from that, the electromechanical prior art DSX functions the same as the well known voice frequency main or intermediate distribution frames in a central office. As in those frames, the equipment and cross-connect blocks of a DSX are hardwired to each other in a predetermined manner so as to accomplish the desired routing for the DS-1 digitial signals. Characteristic of all electromechanical distribution frames whether of the main, intermediate or DSX type, is that all reconfiguration, i.e., changing of the cross-connections, circuit monitoring and testing must be performed manually.
It is, however, desirable that an electromechanical DSX be upgradeable to an electronic DSX. It is also extremely desirable that the upgradeability be capable of being accomplished in a manner such that the electromechanical interconnections can be directly replaced by circuit boards which allow for electronic interconnections. It is also further extremely desirable that this replacement be accomplished in a manner such that the electronic DSX takes up no more floor space than the electromechanical DSX it is replacing. It is also further extremely desirable that the electronic DSX be remotely controllable such that a user can originally configure and change cross-connections, monitor and test by use of a display terminal and keyboard. It is also desirable that the electronic DSX include a jackfield such that the user can patch cross-connections as desired.